Spinning renewal in a working position of an air jet spinning machine occurs after a yarn break or spooling full length of a yarn on a reel. Start of spooling on an empty tube and spinning renewal is performed by an attending device that is arranged displaceably along the working positions of the machine. After stopping at the attended working position, the attending device finds the end of the yarn on the reel or the end of the auxiliary yarn and inserts it into the spinning jet, which is the end of the yarn drawn through, and the yarn of adequate beforehand set length is sucked-in into the vacuum tube. Then the spinning-in begins and new fibres of the spun-out yarn are joined with the end of the yarn drawn off from the vacuum tube inside the spinning jet. It is necessary to brake the yarn being drawn off from the vacuum tube to achieve a quality spin-in.
CZ 2007-629 A3 describes a method and a device for yarn braking, where the device is arranged in proximity to the mouth of the vacuum tube on the attending device of the spinning machine. The yarn is temporarily stored in the vacuum tube, from which it is drawn off afterwards. According to the described method, after moving to the attended operation unit, before commencement of braking, the yarn is inserted to a braking area between two brake friction members, one of which is out of the area at that time. After insertion of the yarn to the braking area, the brake friction members moves closer to the yarn and to each other to such distance, where they act on each other by magnetic force caused by a magnet placed on at least one of them. By the effect of the magnetic force, the brake friction members pull to each other and clamp the yarn with the set force, which causes braking of the yarn.
The device according to CZ 2007-629 A3 comprises two brake friction members, at least one of which is movable to the braking area from a rest position located out of the braking area. Further, at least one of the brake friction members is equipped with a magnet and the other is made of magnetic material. The advantage of the device lies in the fact that there is a good access of the yarn to the braking area and simple induction of the braking force by means of the magnetic force acting between brake friction members.
The disadvantage of both the method and the device according to CZ 2007-629 A3 lies in the fact that the braking force is constant for one yarn diameter and it is difficult to change when, in case it is needed technologically, yarn diameter changes. Regulation is performed by mechanical adjustment of the magnet for a change of the braking force.
The goal of the invention is to simplify mutual coupling of brake friction members and to facilitate changing of setting of the device's braking effect to the yarn.